Tysabri (Natalizumab) Suspension

The Food and Drug Administration (FDA) today issued a public health advisory to inform patients and health care providers about the suspended marketing of Tysabri (nataluzimab) while the agency and the manufacturer evaluate two serious adverse events reported with its use.

Tysabri, which received accelerated approval from FDA in November 2004, is an innovative treatment that represents a new approach to treating patients with relapsing forms of multiple sclerosis (MS).

"FDA worked with the company to make sure this information, even though preliminary, was given to physicians and patients as soon as possible and supports their decision to voluntarily suspend marketing as well as the use of the product in clinical trials. At the same time, FDA continues to believe Tysabri offers great hope to MS patients," said Dr. Steven Galson, Acting Director, FDA's Center for Drug Evaluation and Research (CDER). "Patients being treated with Tysabri should contact their physician to discuss appropriate alternative treatments while these reports are being evaluated," added Dr. Galson.

FDA received a report from Biogen Idec, the manufacturer of Tysabri, of one confirmed fatal case and one possible case of progressive multifocal leukoencephalopathy (PML) in patients receiving Tysabri for MS. FDA was given preliminary information about these cases by Biogen, Idec on February 18, 2005. Details became available to FDA the next week.

PML is a rare, serious progressive neurologic disease usually occurring in immunosuppressed patients. There is no known effective treatment for PML. Although the relationship between Tysabri and PML is not known at this time, because of the serious and often fatal nature of PML, FDA concurred with the company that the drug be voluntarily withdrawn from marketing and that the use of Tysabri in clinical trials be suspended until more is known.

During the review of Tysabri for marketing approval, FDA conducted an intensive analysis of possible adverse events that might be related to effects of the drug on the immune system. No cases of PML were seen in the clinical trials. However, for any approved therapy, new and unexpected adverse events may occur that were not seen in clinical trials. In the case of Tysabri, required post-marketing studies facilitated the rapid reporting and response to this new information.

According to Biogen, Idec, outside of the approximately 3,000 patients who received the drug in clinical trials, approximately 5,000 additional patients with MS have received Tysabri through their primary physician. Because Tysabri was just recently approved, these patients have only received at most a few doses of Tysabri.

The FDA will maintain close contact with the company during the process of understanding the relationship between Tysabri and these two serious adverse events. The company is working on ways to get additional information soon about the possible risks of PML from the patients who have received Tysabri in the clinical trials.

The FDA urges health care providers and patients to report adverse event information to FDA via the MedWatch program by phone (1-800-FDA-1088), by fax (1-800-FDA-0178) or by the Internet at www.fda.gov/medwatch/index.html.